1. Field of the Invention
This invention relates to an inspection probe (pin probe) for use with an apparatus for inspecting conduction of conductors formed in a pattern, for example, on a liquid crystal substrate or semiconductor substrate, and more particularly to an inspection probe which is suitable for use with a probe pin head for the inspection of conduction of conductors which are formed in a high density on such a substrate.
2. Description of the Prior Art
A liquid crystal substrate which makes use of the characteristic of liquid crystal that the light transmittance and reflectance thereof are varied when a suitable voltage is applied thereacross is adopted, for example, in a liquid crystal projecting apparatus for projecting a picture image on a screen. Various product inspections are performed in a procedure of production of such liquid crystal substrates. An exemplary one of conventional conduction inspecting apparatus which perform such product inspections is shown in FIGS. 7 and 8. The conventional conduction inspecting apparatus shown includes a large number of pin probes 32 mounted parallelly in a predetermined spaced relationship from each other on a base 31. When the conduction inspecting apparatus is used, the pin probes 32 are contacted with end portions of conductors 36 formed in a lattice-like pattern on a liquid crystal substrate 35 to inspect electric conduction of the conductors 36. Here, if the pin probes 32 are projected over different distances from the base 31, then it is impossible for them to contact simultaneously and uniformly with all of the conductors 36. To avoid this, each of the pin probes 32 of the conventional conduction inspecting apparatus is formed in such a structure that a body 32a thereof is disposed for advancing and retracting movement in a case 37 and is supported resiliently by a coil spring 38 so that the probe body 32a may be provided with resiliency or normally urged in a direction to be projected from the base 31.
By the way, in the field of liquid crystal substrates adopted for liquid crystal projecting apparatus mentioned hereinabove, increase of the number of picture elements has been proceeded and is being proceeded in order to cope with achievement of a high picture quality, and in recent years, liquid crystal substrates which have 100 to 200 thousand picture elements or up to 300 thousand picture elements have been developed successfully. It is thus forecast that liquid crystal substrates having 800 thousand to 3 million picture elements will be demanded in the near future. Then, the pitch of conductors on a liquid crystal substrate is decreased as such increase of the number of picture elements proceeds. Accordingly, in order to cope with achievement of such high density of conductors, it is necessary to decrease the pitch of pin probes and the diameter of pins of such pin probes.
Further, also in semiconductor logic devices such as integrated circuits, the pitch of conductors is decreased to 50 .mu.m or less or even to 25 .mu.m or less, and in order to cope with such decrease of the pitch of conductors, the diameter of probe pins is naturally demanded to be smaller than 50 .mu.m.
However, such conventional pin probe as described above has a problem that there is a limitation in decrease of the pitch and decrease of the diameter due to structure of them and they cannot cope with the demand described above. In particular, since the conventional pin probe 32 is constituted such that the probe body 32a is accommodated in the case 37 and is supported by the coil spring 38 so that it may have suitable resiliency, the pin probe 32 requires a spacing which is actually occupied by the case 37 in which the coil spring 38 is accommodated, and accordingly, a spacing much greater than a spacing the pin probe 32 actually occupies is required for the pin probe 32. Consequently, there is a base and a limitation in reduction of the pitch of such pin probes, and the pitch is considered to be limited to 300 .mu.m or so.